1. Field of the Invention
The present invention relates to a power saving device and, more particularly, to a power saving wake-up device for wireless mouse.
2. Description of Related Art
A typical wireless mouse uses an internal battery to provide power for its operations. Due to the limited power provided by the battery, the wireless mouse essentially has a power saving mode to save its power. As shown in FIG. 1, when a wireless mouse is not moved for a while, the microprocessor 90 will enter in a doze state and thus turns off most power to make the wireless mouse enter in a power saving mode. Subsequently, in order to determine whether the wireless mouse is moved or not, the microprocessor 90 in the wireless mouse is intermittently waked up to drive the LED 92 of the light emitting unit 91 to emit light. The light is then reflected to the photosensitive unit 93, and the photosensitive unit 93 converts the light into an electronic signal for determining whether the mouse is moved or not. Accordingly, the wireless mouse can be waked up when it is moved, and otherwise, it is kept in the power saving mode. Such a way can reduce the power consumption, but the wireless mouse cannot enter in a completely power saving mode due to the intermittent wake-up operation.
To overcome this, US Patent Publication No. 2004/0008188 entitled “Power saving mechanism for cordless electronic device” uses a shake manner to cause a vibration sensor in a wireless mouse to be a short circuit when the wireless mouse is not used for a while, to thereby produce a trigger signal to wake up the wireless mouse and further improve the power consumption caused by the intermittent wake-up operation. Thus, the wireless mouse can turn off all major power and only keep minor power. However, as shown in FIG. 2, when the wireless mouse is idle, the mercury in the vibration sensor (mercury switch) has an uncertain position, which may stay at position A or B. For the position A, it can cause the vibration sensor to be an open circuit, which does not consume any power when the wireless mouse is in the power saving mode, whereas for the position B, it can cause the vibration sensor to be a short circuit, which still consumes the power when the wireless mouse is in the power saving mode and even consumes power more than that in the normal operation. Accordingly, it is obvious that the vibration sensor cannot normally stay in an open circuit state. Thus, when the wireless mouse is not used for a while and enters in the power saving mode, and the vibration sensor is at a short circuit state (so as to form a short circuit loop), the power can be consumed through the short circuit loop. In this case, the wireless mouse cannot achieve the power saving effect.
Therefore, it is desirable to provide an improved power saving wake-up device for wireless mouse to mitigate and/or obviate the aforementioned problems.